Fuse



m m m M w T m 9 w 2 r E. A. WILLIAMS FUSE Filed May 5, 1934 Inventor:Edwin AWHHams,

His A torneg 5 Patented June 2, 1936 x UNITED STATES PATENT OFFICE FUSEEdwin A. Williams, Springfield, Pa., assignor to General ElectricCompany, a corporation of New York Application May 5, 1934, Serial No.724,041 Claims. (Cl. 200-117) My invention relates to fuses and moreparterminal. To assist in the rapid separation of ticularly to fuses ofthe expulsion type. Expulthe severed ends of fusible element l5 upon thesion fuses have been employed for general use in operation of the fuse,a Compression spring 21 is protecting high voltage circuits andmachinery provided and located between the lower end of 5 e connected insuch high voltage circuits. The tube Ill and contact Ill. The tensionproduced operation of expulsion fuses has proven quite through theintermediary Of Spring 21 is e satisfactory for heavy overloads but somedifllsarily greater than the fusible link I5 is able to culty has beenexperienced in the operation of withstand especially when the fuse isdesigned these fuses with overloads which are slightly in for operationon a circuit at a'relatively low ourexcess of the overloads for whichthe fuse is derent value. Thus to relieve fusible link I5 of this ll)signed to operate. In such cases an overload tension, strain member ISisprovided and secured though relatively light may do considerable damtocontact 24 at one end and terminal 19 at the age by failure of thefuseto operate at all or on other end. Strain member It may consist of afailure of the fuse to operate in a sufliciently wire of a nickelchromium alloy, stainless steel,

0 short time to prevent damage to machinery conor similar materiaL whichwill withstand the relal5 nected in the circuit. v tively high tensioneven when of small cross sec- The object of my invention is to provide afuse tion. It has been the previous practice to proof the expulsion typewhich will operate certainly vide a strain member for the fusibleelement and quickly on relatively light overloads. which is electricallyconnected to the terminals of Q0 What I consider to be novel and myinvention the fusible element. Such a strain member which will be betterunderstood by reference to the folis placed in parallel with the fusibleelement, due

lowing specification and appended claims when to its high specificresistance, carries a relatively considered in connection with theaccompanying 10W P of the Current which passes through drawing in whichFig. 1 is a sectional view of an the fuse link. Upon the blowing of thefusible expulsion fuse embodying my improvements and e t a l f tclJIrent Whih is passing Fig. 2 is a detailed view of a part of thefuse. t u h th fus l nk mu t then pas thr u h t Referring to thedrawing, l0 indicates a tube strain member. It has been found that thesmallof insulating material which forms the housest strain wire whichcan be used to transmit the ing for an expulsion fuse. Ferrules II andI2 are necessary tension and also withstand the usual secured to eachend of tube I0 and are made of operating conditions of vibration, roughhandling, 30 metal and adapted to contact with terminals conetc., willcarry 25 amperes for five minutes before nected in an electric circuit.In order to comit operates. Obviously fuses for operation on ourple'tethe connection of the circuit through the rents below 20 amperes cannotmake use of the fuse, a fuse element I3 which consists of aflexconventional strain member without a great reible conductor I4,fusible link l5, and strain wire duction in its section and acorresponding reduc- 35 I6, is located within tube I0. Flexibleconductor tion in mechanical strength. To reduce both II is connected atone end to a copper shoe 11 the current required to operate the fuse andthe which has a conical end which fits within the time of operationwithout reduction in mechaniconical opening in contact l8. Conductor l4tercal strength, strain member I6 is provided and minates at itsopposite end in a swaged terminal placed. in parallel physically to fuselink 15 but 40 I9. Fusible link i5 consists of a wire 20 which is iselectrically insulated from one terminal of fuse made of one of the wellknown fusible elements link l5. Strain member I6 is directly connectedwhich is readily fusible upon an increase in temby a grommet 28 tocontact 24 by means of bolt perature due to the passage of electriccurrent 25. The other end of strain member i6 is molded therethrough andwhich has a relatively low speas an insert in a plate or member 29 ofinsulating 45 ciflc resistance. Wire 20 is connected at one endmaterial, as better indicated in Fig. 2. The end to a metal terminal 2|which is connected to terof strain member I6 is formed into a loop 30with minal Is by means of a bolt 22. The other end the free end of thestrain member I6 being wound of wire 20 is connected to a terminal 23which is tightly about the adjacent portion of the wire.

connected to a contact 24 by means of a bolt 25. The loop 30 is thenplaced in a mold and insulat- 50 A tube 26 of insulating materialcompletely suring material molded about it in the form of a rounds wire20 between terminals 2| and 23. flat plate with an opening 3|. Opening3! in Contact 24 rests upon the top of tube l0 and is plate 29 isprovided to permit the passage of bolt in engagement with ferrule l I tocomplete con- 22 therethrough to secure the lower end of strain nectionbetween fuse link l3 and the top contact member ii to terminal l9. Thus,strain member 55 I8 is electrically connected to one end of fusible linkI! and is insulated from the other end of the fusible link. By thisarrangement, the strain member is not connected in parallel electricallyto the fusible link as is the usual practice and is not in theelectrical circuit of the fuse element at all as long as the fusiblelink I 5 remains intact. Upon the blowing of the fusible link thecontinuity oi the circuit broken and an arc terminal I! to an is drawnwhich strikes from adjacent portion of strain member I. As is wellknown, an arc seeks the shortest path and so would not strike fromterminal I! to the other terminal 23 of the fusible link I I but asstated above would strike to an ad- Jacent portion of the strain memberIS. The current then flows through a portion of the strain member IS.The combination of the current through the strain member l6 and the arcstriking the strain member will burn the wire through and thus releasethe tension produced by compression spring 21 to immediately separatethe blown ends of the fusible link l5 and positively clear the circuit.It has been found that while the strain member It may not be melted bythe e of 25 amperes through the strain member in less than five minutes,an arc of 1 amperes will burn through the strain member IS in .05second. Thus, by my improved strain member ii the fuse .will operate ata relatively low overload and the blown ends of the fusible link beginto separate within .05 seconds after the melting of the fusible element.At the same time, a mechanically strong fuse which does not requirecareful handling is provided.

The upper end of the fuse tube I0 is closed by means of a cap 32 whichis soldered within the top of ferrule I I to form a waterproof joint.The lower end of tube It is closed by a frangible disc 33 held in theend of ferrule l 2 which is turned in at spaced points 34 to looselyhold the disc 33 in position. Upon operation of the fuse, disc 33 isforced out of the lower end of the tube by the expansion of spring 21.The passage is then open for the fuse element It to be expelled from thelower end of tube Ill. The connection between copper shoe l1 and contactI 8 is collapsed upon movement of the fuse element i3 and so does notinterfere with .the exodus of the fuse element from the tube III.Frangible disc 33 by closing the lower end of tube ill prevents moistureand dust from entering the tube l0 and also serves as a target toindicate the operation of the fuse.

From the foregoing it may be seen that by means of my improved fuse thecurrent required to operate the fuse and the time of operation onrelatively low overloads is greatly reduced without any reduction ofmechanical strength of the fuse element. This reduction in time ofoperation of the fuse greatly reduces the damage which might be done tothe machinery interconnected in the circuit protected by the fuse. Inaddition, my improved fuse insures a completed operation of the fuse onrelatively low overloads to thus greatly reduce the upon failure ofoperation of the fuse.

through the fuse element is damage which might occur What I claim as newand desire to secure by Letters Patent of the United States is:

1. In a fuse having a fuse element under tension, a fusible wireconductor, a metallic strain wire, means for electrically andmechanically connecting said wires together at one end and formaintaining the wires in spaced apart relationship at their connectedends, and means for mechanically connecting the other ends of said wirestogether in non-conducting relationship including a member of insulatingmaterial rigidly attached to one of said wires and secured to said otherend of the other of said wires.

2. In a fuse having a fuse element under tension, a. fusible wireconductor and means for relieving the wire conductor of tensioncomprising a metallic strain wire, means for mechanically andelectrically connecting one end of the strain wire to one end of saidwire conductor with the connected ends of the wires in spaced apartrelationship, a block of insulation material molded securely onto theother end of said strain wire, and means for securing said block ofinsulating material to the other end of said fusible wire conductor withsaid other ends of the wires in spaced apart relationship.

3. In a fuse device, the combination with a fuse tube having a pair ofspaced apart terminals for supporting a fuse element extendinglongitudinally through the tube and having means for tensioning saidfuse element, of a fusible wire conductor connected between saidterminals, a metallic strain wire, means for securing one end of saidstrain wire to one of said terminals in electrical conducting and spacedapart relationship with the adJacent end of said wire conductor, amember of insulating material secured to the other of said terminals,and means for fastening the other end of said strain wire to saidinsulating member with the strain wire extending through said tube inspaced apart relationship with respect to said wire conductor, wherebythe strain wire carries no current while the fusible wire conductor isintact but is severed by an are upon the blowing of the wire conductor.

4. In a fuse having a fuse element under tension, a fusible link,insulating material surrounding said fusible link, and a strain memberfor the electrically connected to one terminal of the fusible link andinsulated from the other terminal of the fusible link whereby the strainmember does not carry any of the current passing through the fuseelement while the fusible link is intact but is severed by an are uponthe blowing of the fusible link.

5. In a fuse having a fuse element under tension, a fusible link,terminals for each end of said fusible link, insulating materialsurrounding said fusible link between said terminals, and a strainmember for the fusible link electrically connected to one of saidterminals and insulated from the other of said terminals whereby thestrain member does not carry any of the current passing through the fuseelement while the fusible link is intact but is severed by an are uponthe blowing 01' the fusible link.

EDWIN A. WILLIAMS.

